Наверняка вы замечали, что в Python есть удобная функция для получения переменной окружения
os.getenv(NAME)
И её "сестра" для создания или изменения переменных окружения
os.putenv(NAME, VALUE)
Но почему-то putenv() не работает как должно. Энвайромент не обновляется!
os.putenv('MYVAR', '1')
print(os.getenv('MYVAR'))
... и ничего 😴
Почему так?
На самом деле энвайромент обновляется, но это значение не добавляется в словарь os.environ.
Откройте исходник функции os.getenv(). Это просто шорткат для os.environ.get()
В то время как putenv() это built-in С-функция.
Словарь os.environ (или точней класс из MutableMapping) создаётся из энвайромента в момент инициализации. Функция putenv() самостоятельно его не изменяет.
В тоже время, когда вы создаёте или изменяете ключ в os.environ, автоматически вызывается putenv() в методе __setitem__().
То есть, технически putenv() всё делает верно, но в os.environ это не отражается. Можно проверить так:
>>> os.putenv('MYVAR', '123')
>>> os.system('python -c "import os;print(os.getenv(\'MYVAR\'))"')
123
Я объявил переменную в текущем процессе и вызвал дочерний процесс, который её унаследовал и получил в составе os.environ.
Аналогично при удалении переменной вызывается еще одна built-in функция unsetenv(), удаляющая переменную из системы.
Итого
▫️ Удобней всего явно обновлять переменные через os.environ
▫️ Есть способ неявно создать/удалить переменную через putenv/unsetenv, что не повлияет на os.environ но изменит энвайромент и передаст изменения сабпроцессам. Но так лучше не делать!
▫️os.environ это просто обертка для built-in функций putenv() и unsetenv().
#basic
😄Pretty
➖➖➖➖➖➖
🔘Pretty as an adjective means 'attractive, especially when talking about girls or women'.
Margo always tells her daughter that she's pretty.Margo always tells her daughter that she's pretty.
🔜Jacob's mum is really pretty.
🔘Pretty is also used to talk about things that are 'pleasant to look at in a delicate or charming way'. While this is often connected to females, it can also be used to describe something like 'a view'.
🔜There's a very pretty view at the top of that hill.
🔜My friend moved out of the city and bought a pretty cottage in the countryside.
🔘As an adverb, pretty can be an informal way of saying 'quite' or 'rather'.
🔜The house was built recently, it's pretty new.
🔜I enjoyed that film, it was pretty good.
🔘We can also use pretty to give emphasis.
🔜We went to bed at 2am, so we were pretty tired.
🔜I'm pretty angry right now, so don't talk to me.
#Pretty👨🏫@America
➖➖➖➖➖➖➖➖➖➖➖➖
🆕 Crypto News @Money
😁 Crypto Game @Egame
🇺🇸 US News @America
🇯🇵 Japan News @Japan
🇦🇪 UAE News @Dubai
▶️ Popular Movies @Videos
😜 Best Funny Video @Funnys
😄Pretty
➖➖➖➖➖➖
🔘Pretty as an adjective means 'attractive, especially when talking about girls or women'.
Margo always tells her daughter that she's pretty.Margo always tells her daughter that she's pretty.
🔜Jacob's mum is really pretty.
🔘Pretty is also used to talk about things that are 'pleasant to look at in a delicate or charming way'. While this is often connected to females, it can also be used to describe something like 'a view'.
🔜There's a very pretty view at the top of that hill.
🔜My friend moved out of the city and bought a pretty cottage in the countryside.
🔘As an adverb, pretty can be an informal way of saying 'quite' or 'rather'.
🔜The house was built recently, it's pretty new.
🔜I enjoyed that film, it was pretty good.
🔘We can also use pretty to give emphasis.
🔜We went to bed at 2am, so we were pretty tired.
🔜I'm pretty angry right now, so don't talk to me.
#Pretty👨🏫@America
➖➖➖➖➖➖➖➖➖➖➖➖
🆕 Crypto News @Money
😁 Crypto Game @Egame
🇺🇸 US News @America
🇯🇵 Japan News @Japan
🇦🇪 UAE News @Dubai
▶️ Popular Movies @Videos
😜 Best Funny Video @Funnys
http://www.enlistq.com/10-python-idioms-to-help-you-improve-your-code/
If you have ever tried to learn a new language (not a programming language), you know that we always think in our native language before we translate it to the new language. This can lead to you forming some sentences that don’t make sense in the new language but are perfectly normal in your native language. For example, in a lot of languages, you ‘open’ an electronic gadget such as fan, AC or cell phone. When you say that in English, it means to literally open the gadget instead of turning it on.
The same is true for programming languages. As we pick up new languages, such as #python, we are using our prior knowledge of programming in another language (q, java, c++ etc) and translating that to python. Many times, your code will work but it won’t be ‘#pretty’ or #fast. In python terms, your code won’t be ‘#pythonic’.